Bonjour

h (x) = f (x) + g (x)

h (x) = x² - 8 (x + 3) + (- 9 + x) (3x + 7)

h (x) = x² - 8x - 24 + 3x² - 27x - 63 + 3x² + 7x

h (x) = x² + 3x² + 3x² - 8x - 27x + 7x - 63 - 24

h (x) = 7x² - 28x - 87.